(1) Field of the Invention
This invention relates to a process for producing a super smooth printing surface of foil laminated paperboard used in the folding carton industry. More particularly, it relates to smoothing the foil printing surface of a foil laminated paperboard by passing the laminate through a nip formed by a hard roll and a resilient roll.
(2) The Prior Art
Heretofore paperboard suppliers have performed calendering operations on paperboard to obtain a commercially accepted smoothness of the paperboard for printing or foil laminating for the general trade industry. However, when a super smooth foil laminated printing surface is desired the present alternative is to use a coated paperboard stock, which requires a special coating to be applied to the paperstock surface in a separate operation. This separate step increases the costs of the paperboard stock.
Prior art attempts to provide a smooth printing surface having primarily involved calendering or super calendering operations to smooth coated papers. One such example is U.S. Pat. No. 3,336,862 to Brundige et al which teaches calendering a web of double coated paper using a calender stack having a resilient covered roller. The resilient rollers of Brundige et al are used primarily to increase the gloss of the coated paper; whereas, the resilient roller used in the process of the present invention does not calender but serves to smooth the surface of a foil laminate.
U.S. Pat. No. 3,230,867 to Nelson describes a calendering mechanism which includes a resilient subordinate roll, e.g., a cotton filled auxiliary roll to help calender, and a heated metal roll, and may be used in connection with the paper machine or on a coating machine. The cotton filled rolls described in Brundige et al and Nelson do not perform well in the process of the present invention because the cotton rolls transfer any imperfection in the roll surface to the paperboard material because the cotton roller surfaces are not sufficiently hard and resilient to resist imperfections.